mye35171_ch24_281-300.indd Page 281 10/12/10 11:11/208/MHSF219/myr35171_disk1of1/0078035171/myr35171_pagefiles AM user-f494 MODULE 24 ❖ The Nature and Nurture of Aggression lthough Woody Allen’s tongue-in-cheek prediction that “by 1990 Akidnapping will be the dominant mode of social interaction” went unfulfilled, the years since have hardly been serene. The horror of 9/11 may have been the most dramatic recent violence, but in terms of human lives, it was not the most catastrophic. About the same time, the human carnage from tribal warfare in the Congo was claiming an esti- mated 3 million lives, some of the victims hacked to death with machetes, many others dying of starvation and disease after fleeing in terror from their villages (Sengupta, 2003). In neighboring Rwanda, where some 750,000 people—including more than half the Tutsi population—were slaughtered in the genocidal summer of 1994, residents are all too famil- iar with this human capacity for carnage (Dutton & others, 2005; Staub, 1999). So are the people of Sudan, where war and genocide have claimed 2.5 million people (Clooney & others, 2008). Worldwide, more than $3 billion per day is spent on arms and armies—$3 billion that could feed, educate, and protect the environ- ment of the world’s impoverished millions. During the last century, some 250 wars killed 110 million people, enough to populate a “nation of the dead” with more than the combined population of France, Belgium, the Netherlands, Denmark, Finland, Norway, and Sweden (Figure 24-1). com/m e. y h e h r s The tolls came not only from the world wars but also from genocides, m e . s p w 6 w e including the 1915 to 1923 genocide of 1 million Armenians by the Otto- w Activity man Empire, the slaughter of some 250,000 Chinese in Nanking after it 24.1 had surrendered to Japanese troops in 1937, the 1971 Pakistani genocide 281 mye35171_ch24_281-300.indd Page 282 08/12/10 4:17 AM user-f494/208/MHSF219/myr35171_disk1of1/0078035171/myr35171_pagefiles 282 PART FOUR SOCIAL RELATIONS War-related deaths over the centuries (millions) 120 100 80 60 40 20 0 1st to 16th 17th 18th 19th 20th 15th (to 1995) Century FIGURE 24-1 The bloodiest century. Twentieth-century humanity was the most educated, and homicidal, in history (data from Renner, 1999). Adding in genocides and human- made famines, there were approximately 182 million “deaths by mass unpleasant- ness” (White, 2000). By the century’s end, such deaths were declining (Human Security Centre, 2005). of 3 million Bangladeshis, and the 1.5 million Cambodians murdered in a reign of terror starting in 1975 (Dutton & others, 2005; Sternberg, 2003). As Hitler’s genocide of millions of Jews, Stalin’s genocide of millions of Russians, Mao’s genocide of millions of Chinese, and the genocide of millions of Native Americans from the time of Columbus through the nineteenth century make plain, the human potential for extraordinary cruelty crosses cultures and races. To a social psychologist, aggression is physical or verbal behavior intended to cause harm. This definition excludes unintentional harm such as auto accidents or sidewalk collisions; it also excludes actions that may involve pain as an unavoidable side effect of helping some- one, such as dental treatments or—in the extreme—assisted suicide. It includes kicks and slaps, threats and insults, even gossip or snide “digs.” Instrumental aggression aims to injure, too—but only as a means to some other end. Most terrorism is instrumental aggression. “What nearly mye35171_ch24_281-300.indd Page 283 08/12/10 4:17 AM user-f494/208/MHSF219/myr35171_disk1of1/0078035171/myr35171_pagefiles MODULE 24 THE NATURE AND NURTURE OF AGGRESSION 283 all suicide terrorist campaigns have in common is a specific secular and strategic goal,” concludes Robert Pape (2003) after studying all suicide bombings from 1980 to 2001. That goal is “to compel liberal democracies to withdraw military forces from territory that the terrorists consider to be their homeland.” Terrorism is rarely committed by someone with a psychological pathology, note Arie Kruglanski and Shira Fishman (2006). Rather, it is a strategic tool used during conflict. In explaining the aim of the 9/11 attacks, Osama bin Laden noted that for a cost of only $500,000 they inflicted $500 billion worth of damage on the American economy (Zakaria, 2008). Most wars are instrumental aggression. In 2003, American and British leaders justified attacking Iraq not as a hostile effort to kill Iraqis but as an instrumental act of liberation and of self-defense against presumed weapons of mass destruction. Hostile aggression is “hot”; instrumental aggression is “cool.” T HEORIES OF AGGRESSION Is Aggression an Instinct? Philosophers have debated whether our human nature is fundamentally that of a benign, contented, “noble savage” or that of a brute. The first view, argued by the eighteenth-century French philosopher Jean-Jacques Rousseau (1712–1778), blames society, not human nature, for social evils. The second idea, associated with the English philosopher Thomas Hobbes (1588–1679), credits society for restraining the human brute. In the twen- tieth century, the “brutish” view—that aggressive drive is inborn and thus inevitable—was argued by Sigmund Freud in Vienna and Konrad Lorenz in Germany. Freud speculated that human aggression springs from a self- destructive impulse. It redirects toward others the energy of a primi- tive death urge (the “death instinct”). Lorenz, an animal behavior expert, saw aggression as adaptive rather than self-destructive. The two agreed that aggressive energy is instinctive (unlearned and uni- versal). If not discharged, it supposedly builds up until it explodes or until an appropriate stimulus “releases” it, like a mouse releasing a mousetrap. The idea that aggression is an instinct collapsed as the list of sup- posed human instincts grew to include nearly every conceivable human behavior and scientists became aware how much behavior varies from person to person and culture to culture. Yet, biology clearly does influ- ence behavior just as nurture works on nature. Our experiences interact with the nervous system engineered by our genes. mye35171_ch24_281-300.indd Page 284 08/12/10 4:17 AM user-f494/208/MHSF219/myr35171_disk1of1/0078035171/myr35171_pagefiles 284 PART FOUR SOCIAL RELATIONS Neural Influences Because aggression is a complex behavior, no one spot in the brain con- trols it. But researchers have found neural systems in both animals and humans that facilitate aggression. When the scientists activate these brain areas, hostility increases; when they deactivate them, hostility decreases. Docile animals can thus be provoked into rage, and raging animals into submission. In one experiment, researchers placed an electrode in an aggression- inhibiting area of a domineering monkey’s brain. A smaller monkey, given a button that activated the electrode, learned to push it every time the tyrant monkey became intimidating. Brain activation works with humans, too. After receiving painless electrical stimulation in her amygdala (a part of the brain core), one woman became enraged and smashed her guitar against the wall, barely missing her psychiatrist’s head (Moyer, 1976, 1983). Does this mean that violent people’s brains are in some way abnor- mal? To find out, Adrian Raine and his colleagues (1998, 2000, 2005, 2008) used brain scans to measure brain activity in murderers and to measure the amount of gray matter in men with antisocial conduct disorder. They found that the prefrontal cortex, which acts like an emergency brake on deeper brain areas involved in aggressive behavior, was 14 percent less active than normal in murderers (excluding those who had been abused by their parents) and 15 percent smaller in the antisocial men. As other studies of murderers and death-row inmates confirm, abnormal brains can contribute to abnormally aggressive behavior (Davidson & others, 2000; Lewis, 1998; Pincus, 2001). Genetic Influences Heredity influences the neural system’s sensitivity to aggressive cues. It has long been known that animals can be bred for aggressiveness. Some- times this is done for practical purposes (the breeding of fighting cocks). Sometimes breeding is done for research. Finnish psychologist Kirsti Lagerspetz (1979) took normal albino mice and bred the most aggressive ones together; she did the same with the least aggressive ones. After repeating the procedure for 26 generations, she had one set of fierce mice and one set of placid mice. Aggressiveness also varies among primates and humans (Asher, 1987; Bettencourt & others, 2006; Denson & others, 2006; Olweus, 1979). Our temperaments—how intense and reactive we are—are partly brought with us into the world, influenced by our sympathetic nervous system’s reactiv- ity (Kagan, 1989; Wilkowski & Robinson, 2008). A person’s temperament, observed in infancy, usually endures (Larsen & Diener, 1987; Wilson & Matheny, 1986). A child who is nonaggressive at age 8 will very likely still be a nonaggressive person at age 48 (Huesmann & others, 2003). mye35171_ch24_281-300.indd Page 285 08/12/10 4:17 AM user-f494/208/MHSF219/myr35171_disk1of1/0078035171/myr35171_pagefiles MODULE 24 THE NATURE AND NURTURE OF AGGRESSION 285 Blood Chemistry Blood chemistry also influences neural sensitivity to aggressive stimulation. Alcohol Both laboratory experiments and police data indicate that alco- hol unleashes aggression when people are provoked (Bushman, 1993; Taylor & Chermack, 1993; Testa, 2002). Consider: • In experiments,